Control of grid glow tubes



atented Jan. 5, 1932 UNITED STATES PATENTpOFFICE JOHN VICTOR BREISKY, FPITTSBURGH, AND ELLIS O. ERICKSON, OF WILKINSBURG,

PENNSYLVANIA., ASSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURINGCOMPANY, AKCORPORATIO'N OF PENNSYLVANIA CONTROL OF GRID 'GLOW TUBESApplication led January 23, 1929. Serial No. 334,451.

Our invention relates to control circuits and Amore particularly tocontrol circuits comprising a grid glow tube.

An object of our invention is to provide a relatively simple and directcontrol system that shall embody a light-sensitive means as the primarycontrol element and that shall i embody a grid glow tube as an immediatecontrolling means for a Work circuit, an indicating or a signal device,or, in fact, any energy-translating device.

In practicingr our invention, we provide in a specific form thereof incombination with a work circuit, a contactor for controlling the same,the actuating coil of the contactor being controlledLby a grid glowtube. The grid glow tube is, in turn, controlled by the variation in theenergization of one or more of a plurality of photo-electric cells.

ln the single sheet of drawings,

Figure 1 is a diagram of connections of a system embodying ourinvention,

Fig. 2 is a diagram of connections of a modified system embodying ourinvention,

Fig. 3 is a diagram of connections of another modification embodying ourinvention, and

Fig. 4 is a diagram of connections of a still further system embodyingour invention.

Referring more particularly to Fig. 1 of the drawings, We havethereillustrated a grid glow tube l11 connected in series electriccircuit with the actuating coil 12 of a contactor 13 and with acurrent-limiting resistor 14. The tube 11 comprises an anode 16, acathode 17 and a control electrode 18, all located within a suitablecasing 19.

The grid glow tube, illustrated in general only, is of the type in whichthe-superficial arca of the cathode 17 is large and in which the anode16 is relatively very small, both in volume and in superficial area. Thecontrol electrode 18 is also relatively very small in volume and inareaand is located relatively very close to the anode 16.

A tube or electrical-discharge device of this kind has the property ofbeing substantially non-conducting, so long as the control electrode. 18is completely insulated relatively to the two main elctrodes and for allvoltvalue traversing the tube, ,so long as the control electrode isinsulated, as described above.

If, however, the control electrode be momentarily connected to the anodeeither directly or through a leakage impedance path of suitable value,the blocking charge will be dissipated, and the tube will becomeelectricconducting substantially instantaneously.

It is to be noted that the tube has, inherently, a fully conducting andsubstantially non-conducting condition only as regards the directcontrol of a relay coil, or of an energytranslating device of any kindoperatively associated with the grid-gloW-tube circuit and that it doesnot haveany intermedia-te variable operating condition, suchas does athermionic amplitier tube.

An 'impedance 22, which is preferably made adjustable and may comprisean inductance, a capacitance, or a resistance or any combination thereofis connected between the anode 16 and the control electrode 18. For theapparatus shown in Figs. 1 and 3, a resistance of approximately 100megohms is preferably used, while for the apparatus shown in the othertwo figures, the capacity or inductance used should have a value ofsutlicient magnitude to yield this impedance for the frequency of theexciting potential.

It is interesting to note that variations in the magnitude of theimpedance 22 vary the voltage required to cause a discharge in the gridglow tube. Since the break-down voltage depends on the photo-cellillumination, it is possible, by varying the impedance, to vary thesensitivity of the Whole system. A

lplurality of light-sensitive or photo-electric cells 23 are connectedin circuit in series relation to each other, and the anode of one of thecells is connected to the control electrode 18 of the glow tube. Thecathode of the last cell in the series is connected to the negativeterminal of the battery 21, as well as to one terminal of the actuatingcoil 12.

A supply circuit 24 is illustrated as embodying a plurality ofconductors, u source of supply 26 of electric energy and acontactbridging member 27 actuated by a core mem ber 28 which isenergized by the coil 12. 1t is to be understood that since any type orkind of work circuit indicating an energytranslating device isrepresented by the relay 13, no specific illustration thereof isbelieved to be necessary'.

A source of radiant energy for the photo- 'sensitive cells 23 comprisesan incandescent lamp 29, a source of supply 31 therefor and a ycontrolswitch 32, which may be manually actuated.

Referring more particularly to Fig. 2 of the drawings, we have thereshown a grid glow tube 11 connected in series-circuit rela- -tion to acurrent-limiting resistor 14 and an pedance 22 is connected between theelectrode 18 and the junction point of the actuating winding l2 and ofthe secondary winding 33. A similar source of radiant energy 29 isprovided, as hereinbefore set forth in connection with Fig. 1 of thedrawings.

Referring more particularly to Fig. 3 of the drawings, we have thereillustrated a plurality of photo-sensitive cells 23 connected inthecircuit inparallel relation to each other, the other elements and theconnectionthereof being the same as hereinbefore set forth in connectionwith Fig. 1.

Referring more particularly to Fig. 4 of the drawings, we have thereillustrated substantially the same elements as are shown in Fig. 2 ofthe drawings, .with the exception that the photo-electric cells 23 areconnected in the circuit in parallel relation to each other instead ofin serieseleetric-circuit relation. All'the other elements of the systemand circuit are substantially the same.

Referring now to Figs. 1 and 3 of the drawings, when a grid glow tube ofthe kind preferred by us and hereinbefore described is connected in themanner shown, and as long as the photo-electric cells are energized bythe light source 29, the grid glow tube will be nonconductingso thatsubstantially no current will traverse it, the resistor 14 and theactuating coil 121. rllhe work circuit will, there' fore, be normallydeenergized.

lt may be well to briefly set forth the reason for the grid glow tubebeing substantially electrically non-conducting. lt may be noted that ashunt circuit is established thereto, beginning at the positive terminalof the battery 2l, through the impedance 22 and the energizedphoto-electriccells 23, to the other terminal of the battery. A. currentof a pl'edetermined value will traverse this circuit, and a certainpotential drop will exist across the impedance 22 so that the Voltage atthe lower terminal thereof and', therefore, at the control electrode 18,will be lower than the potential of the anode 16. 'lhis is the conditionwhich must exist' to accumulate a blocking charge on the controlelectrode, and the tube is therefore non-conducting.

Since the impedance 22 is constant, the drop in potential across thisimpedance and, consequently, the drop in potential between the anode 1Gand the control electrode 18 is determined by the current that iiows inthe impedance and increases with an increase in current.

The potential of the anode 16, on the other hand, is invariant and, as aconsequence, an increase in the current through the impedance 22 causesa decrease in the potential of the control electrode 18, that is to say,it causes a decrease in the force tending to draw electrons from theanode.

For a large enough Value of the impedance current, the potential of thecontrol electrode is rendered so low that current is not drawn from theanode. Such a state of atlairs exists when the photo-cells are under theinfluence of total light flux sutiicient to reduce this inipedance tothe requisite value.

On the other hand, if the radiant energy impinging on one or more of thephoto-cells is decreased in value, the impedance of the cell isincreased, the'current through the impedence decreased, and thepotential of the control electrode is increased. For a suiiicientdecrease in radiant energy, the potential of the control electrode isincreased enough to cause an electric breakdown of the galpw tube.

The tube'will then become fully'co'iidueting andthe actuating coil 12will be energized, whereby the work circuit 24 or its equivalentenergy-translating device will be energized.

It should be noted, however, that a breakdown of the glow-tube may beregarded simply as a decrease in the impedance of the circuit shuntingthe photo-cell circuit and, consequently, results in a further decreasein the current in this circuit. If, then, the photocells are returned totheir original state of excitation, the current in the photo-cellcircuit is still considerably smaller than it originally was and, as aresult, a discharge conv tinues in the tube 11.

The tubel will, therefore, continue in its energized andelectric-conducting condition after it has been put in that condition,and

the relay 13 need not be particularly fast in 'order to be actuated inthe proper manner.

In order to render the tube non-conducting, it is necessary to reducethe supply-circuit voltage to a value below the critical value, or tointerrupt the circuit.

Referring to Figs. 2 and 4 of the drawings, the system there shown willoperate to cause the tube` 1l to be normally conducting so long as thephoto-electric cells 23 are. suitably enerj glzcd by the source 29.

Since the glow-tube and the photo-cells conduct currents in only onedirection, the secondary 33 of the transformer 34 may be regarded as abattery, simil'ar in polarity to the battery 21 of Figs. l and 3, duringits active period of operation. It should, however, be borne in mindthat the -polarizing voltage is only periodically applied.

It is seen that, forthe circuit shown in Figs. 2 and 4, the lowerterminal of the impedance 22 is substantially invariant, and,consequently, for an increase in current in the impedance 22, theotential of the electrode 13 is increased. ence, in this case, anincrease in the light flux impinging on the photo-cells results in anincrease in the potential of the electrode and, consequently, theglow-tube breaks down if sufiicient light is supplied to decrease theimpedance of the photo-cells to the requisite amount.

The work circuit, therefore, is normally closed. lt is open when theradiations exciting one or more of the cells experience a decreasesuflicient to cause the potential of the control electrode to drop belowthe blocking point, thus causing the tube to become non-conducting. Thisstate of affairs will cause the coil 12 to become deener ized and resultin a movement of the bridging member 27 to interrupt the work circuit.

On the other hand, since the potential producing the discharge is, forthe apparatus shown in Figs. 2 and 4, periodically Zero for a certaininterval of time, it is possible, by sufiiciently decreasing the radiantenergy impilrging on the cells, to extinguish the glow tu e.

@ne of the uses of a system of the kind shown in Fig. 2 is' for theexamination of moving objects or 'for the supervision of a space inwhich smoke and fire may occur, as in a smoke recorder. If smoke shouldbe generated between the light source 29 and one or more of the cells23, they would be deenergized to a greater or lesser extent and, ifsufliciently deenergized, the tube would become electricallynon-conducting, as explained above. As the smoke may be of momentaryduration only, it is necessary that the relay 13 be very fast in itsoperation, in order thatit may operate i'n the relatively, short periodof time in which a change in the electricfconducting condition of thetube exists.

Referring more particularly to Fig. 3 of the drawings, we have thereshown a system of the same general kind as described hereinbefore inconnection with Fig. 1 of the drawings, except that the photo-sensitivecells are connected in parallel, an'd a change in the electricalpotential of the electrode 18 is effected by varying the intensity ofthe radiant energy reaching one or more of the shunt-connected cells.If, for instance, one of the cells becomes electrically non-conductingbecause of the inter-position of smoke or an opaque or substantiallyopaque object, the conditions existing in the shunt circuit may bevaried sufliciently thereby to cause the tube 11 to becomeelectric-conducting. The impedance 22 is made adjustable in order thatthe circuit may be adapted to the particular conditions attendant uponthe use of a plurality of parallel-connected photo-sensitive cells, aswell as to the actual operating conditions.

Referring to Fig. 4 of the drawings, the action of this system issubstantially the same as was hereinbefore set forth in connection withFig. 2 of the drawings and `as modified by the parallel connection ofthe photo-sensitive cells.

It may be noted also, that the systems illustrated in Figs. 3 and 4 mayalso be operated With the light-sensitive cells normally deenergizedwhen an alternating-current source of energy is used. .This would be thecase if a moving web of opaque material were being examined for openingstherein or for a break such as may occur in paper manufacture.

The system of Fig. 3 will operate on an alternating-current source withthe grid glow tube normally electric-conducting, and it would becomenon-conducting upon energization of one or more of the cells 23, and therelay or its equivalent energy-translating device would be actuated bythe change in the condition of the grid glow tube.

The grid glow tube, in the system shown in Fig. 4, when connected to analternatingcurrent source, would be non-conducting if all of the cells23 were deenergized, and the tube would become conducting uponenergization of any one or more of the cells 23. A work circuit orenergy-translating device would then be actuated or controlled by suchchan-ge of condition.

It may be further noted that it is not necessary that a single source ofenergybe provided for both the grid glow' tube and the light-sensitivecells, or that the voltage of the source be the source for both elementsnamed above. Thus, a tap 41'may be provided on the battery 21, shown inFigs. 1 and 3, and the cell or cells may be connected to the tap insteadof to the end one of the series of battery cells.

It may be noted that, when a direct-current source of energy is used, itis not necessary to have an extremely fast operating relay, as thesystem, or particularly the tube, is nonreversible, that is, once itbecomes conducting it remains so until a major change is made in theoutside or in the inside conditions of the circuit.

rl`he use of the adjustable impedance 22, connected as shown, permits otcontrolling the sensitivity of the tube so that minor variations in theelectricalconditions of the circuit or in the operating conditions willnot effect a change in the condition of the tube, except and unless suchchanges be ot the proper magnitude ot which it is desired to takecognizance.

When an alternating-current source of energy is used, the relay shouldbe extremely fast, particularly if the operation supervised by thesystem is such as to inherently permit of very tast, abnormal operatingconditions which are to be recognized in the work circuit.

A grid glow tube of the kind illustrated and described, permits of beingtraversed by a current on the order of milli-amperes and, therefore, itis unnecessary to use a thermionic amplifier tube, as has been doneheretofore, our circuits thus being relatively much more simple and morerugged and effecting the same control in a somewhat different manner.

Ye desire it to be understood that when the termenergy-translatingdevice is used in .the claims, any controllable meanssuch as a relay ora signal device actuable by electric current, is included.

Various modifications may be made in the system embodying our inventionwithout departing from the spirit and scope thereof,

'and we. desire, therefore, that only such limitations shall be placedthereon as are imposed by the prior art or are set forth in the appendedclaims.

XVe claim as our invention:

l. In van electric circuit, in'combination, an energy-translatingdevice, a glow tube having two main electrodes and a control electrodeand having inherently a fully conducting and a substantiallynon-conducting condition only, means for connecting the main electrodesand the energy-translating device in electric circuit with a source ofelectric energy, means for controlling the energization of saidenergy-translating device and tube comprising a series-connectedimpedanceand a plurality of light-sensitive cells, means for connectingthe junction of the impedance and the cells to the control electrode.and the outer terminals of another of the cells and the impedance to therespective main electrodes.

2. In an electric circuit, in combination, an energy-translating device,a glow tube having, inherently, a fully conducting and a substantiallynon-conducting operating condition only and embodying two mainelectrodes and a control electrode, means for controlling the operatingcondition of said tube comprising a plurality of light-sensitive cellselectrically connected to the control electrode and one of the mainelectrodes, and means for controlling the sensitivity of the glow tubecomprising an impedance electrically connected to the control electrodeand the other main electrode,

In an electric circuit, in combination, an energy-translating device, aglow tube having, inherently, a fully conducting and a substantiallynou-conducting operating condition only and embodying two mainelectrodes and a control electrode, means for controlling the operatingcondition of said tube comprising a plurality ot' light-sensitive cellselectrically connected to the control electrode and one of the mainelectrodes, and means cooperating with said cells to ctl'ect a. changein the operating condition of said-tube only upon the occurrence of achange of predetermined magnitude in the electrical condition of one ormore ot said cellls, said means comprising an impedance electricallyconnected to the control electrode and the other main electrode.

4. In an electric circuit, in combination, an energy-translating device,a glow tube connected in electric circuit with said energytranslatingdevice and embodying two main electrodes and a control electrode andhaving, inherently, a fully conducting and a substantiallynon-conducting operating condition only, and control means tor said tubeconiprising a plurality of series-connected lightsensitive cells. meansfor electrically connecting them to the control electrode and one of themain electrodes, an impedance, and means for electrically connecting itto the control electrode and to the other main electrod-e.

5. In an electric circuit. in combination, an energy-translating device,a glow tube having two main electrodes and a control elect-rode andhaving inherently a fully conducting and a substantially non-conductingcondition only, means for connecting the main electrbdes and theenergy-translating device in electric circuit with a source ofelectricenergy, means for controlling the energization of saidenergy-translating device and tube comprising a series-connectedimpedance and a light-sensitive device, means for connecting thejunction of the impedance and the light-sensitive device to the controlelectrode. and the outer terminals of the light sensitive device and theimpedance to the respective main electrodes.

6. In an elect-ric circuit, in combination, an energy-translatingdevice, a glow tube having, inherently, a fully conducting and asubstantially non-conducting operating condition only and embodying twomain electrodes and a control electrode, means for controlling theoperating condition of said tube comprising a light-sensitive cellelectrically connected to the control elect-rode and one of the mainelectrodes, and means cooperating with said cell to effect a change inthe operating condi.- tiou of said tube only upon the occurrence of achange of predetermined magnitude in the electrical condition of saidcell, said means comprising' an impedance electrically connected to thecontrol electrode and the other main electrode. v

7; In an electric circuit, irl-combination, an energy-translatingdevice, a glow tube having, inherently, a fully conducting and asubstantially non-conducting operating condition only and embodying, acathode, an anode and a control electrode, means for controlling theoperating condition of said tube comprising a light-sensitive cellelectrically connected to the control electrode and the cathode, andmeans cooperating with said cell to effect a change in the operatingcondition of said tube only upon the occurrence of a change ofpredetermined magnitude in the electrical condition of said cell, saidmeans comprising an impedance electrically connected to the controlelectrode and the anode.

In testimony whereof, we have hereunto subscribed our names this 18thday of January, 1929. v

JOHN VICTOR BREISKY. ELLIS O ERICKSON.

